by Mahnke D

Click here to view an animated version of this procedure.


A colonoscopy is an exam of the colon. The exam is done with a long, thin tube called a scope. This scope has a tiny camera on the end which allows the doctor to see the walls of the colon.

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Reasons for Procedure

The colon is the last part of your intestines. A colonoscopy is used to look for and treat problems in the area. The most common reasons for a colonoscopy are to:

  • Look for cause of belly pain, bleeding, or problems with passing stool
  • Look for signs of colon cancer ; may also be a part of treatment
  • Look for and remove colon polyps ; some polyps can become cancer
  • Take sample of colon to look at under a microscope (known as a biopsy )
  • Stop bleeding in the colon
  • See if treatment for inflammatory bowel disease is working as it should

Possible Complications

Problems are rare, but all procedures have some risk. Your doctor will talk to you about possible problems such as:

The risk of problems is increased with:

  • Smoking
  • Heart or kidney problems
  • Treatment with certain medicine, including aspirin and other blood-thinning drugs
  • Prior surgery in the area
  • Active colitis , diverticulitis , or other acute bowel disease
  • Radiation therapy in the past

What to Expect

Prior to Procedure

The doctor may ask you about your past health. Other steps may include:

  • Review of any medicine or supplements. You may be asked to stop taking some medicine up to 1 week before the procedure.
  • Stool test to look for blood .
Emptying the Colon

The colon must be cleaned out. Any stool left in the colon will block the view. This process may start several days before the procedure. The doctor will give specific instructions. Bowel movements may be encouraged with 1 of these steps:

  • Enemas—fluid is passed into the rectum
  • Laxatives—medicine taken by mouth or placed into rectum
  • Oral cathartic medicine—a fluid that you drink

In the day before the procedure:

  • Solid foods will need to be avoided. This includes milk or cream in coffee.
  • Only clear liquids are allowed. This includes water, coffee without cream, ginger ale, apple juice, and sports drinks. Avoid red sports drinks.
  • Gelatin or popsicles are allowed as long as they are not red.
  • Alcohol needs to be avoided.
  • Insulin medicine may need to be changed.

Comfortable clothes should be worn on the day of the colonoscopy. A ride home will be needed.


Medicine may be given to help you relax. You'll probably feel sleepy.

Description of the Procedure

You will lie on your left side. Your knees will be drawn up toward your chest. The scope will be slowly inserted into the rectum. It will inject air into the colon to help open the area. The doctor will slowly pass the scope up into the colon. The camera on the scope will send images to a monitor on the room. The doctor will be able to see the walls of the colon as the scope moves through.

Other tools can be passed through the scope. The tools may remove a sample of tissue or polyps. The tissue can then be sent for testing. The scope will be removed once the doctor is done.

How Long Will It Take?

Less than 1 hour

Will It Hurt?

There may be some discomfort when the scope is inserted. Some cramping or lower belly pain can happen during the procedure. Medicine will help to ease discomfort. Some will sleep through the procedure.

Gas pains and cramping are common after. These pains should go away with the passing of gas.

Post-procedure Care

You will remain at the care center until you are able to leave. It may be 1 to 2 hours. It is best to take it easy for the rest of the day. Most can return to normal activity within 24 hours.

It may take 1 to 2 weeks to get results back from tissue sample. Other tests may be needed.

Call Your Doctor

Let your doctor know if recovery is not going as expected or you have any of the following:

  • Bleeding from your rectum—more than your doctor said you may see
  • Black, tarry stools
  • Severe belly pain
  • Hard, swollen belly
  • Signs of infection, including fever or chills
  • Problems passing gas or stool
  • Coughing, shortness of breath, chest pain, severe nausea or vomiting

If you think you have an emergency, call for emergency medical services right away.


American Society for Gastrointestinal Endoscopy 

National Institute of Diabetes and Digestive and Kidney Diseases 


American Gastroenterological Association 

American Society for Gastrointestinal Endoscopy 


Canadian Association of Gastroenterology 

Canadian Digestive Health Foundation 


Colonoscopy. EBSCO DynaMed website. Available at:  . Updated October 22, 2019. Accessed January 10, 2020.

Colonoscopy. National Institute of Diabetes and Digestive and Kidney Diseases website. Available at: Updated July 2017. Accessed January 10, 2020.

National Cancer Institute. Colon cancer treatment (PDQ®)-patient version website. NIH external link. Updated January 31, 2020. Accessed January 10, 2020.

6/2/2011 DynaMed's Systematic Literature Surveillance  : Mills E, Eyawo O, Lockhart I, Kelly S, Wu P, Ebbert JO. Smoking cessation reduces postoperative complications: a systematic review and meta-analysis. Am J Med. 2011;124(2):144-154.

Revision Information

  • Reviewer: EBSCO Medical Review Board Daus Mahnke, MD
  • Review Date: 09/2019
  • Update Date: 10/16/2020